(a) Field of the Invention
The present invention relates to a sensor, a thin film transistor array panel including the sensor, and a display panel including the sensor. More particularly, the present invention relates to an improved temperature sensor, a thin film transistor array panel including the temperature sensor, and a display panel including the temperature sensor.
(b) Description of the Related Art
Display devices used for monitors of computers and television sets generally include self-emitting display devices such as organic light emitting displays (“OLEDs”), vacuum fluorescent displays (“VFDs”), field emission displays (“FEDs”), and plasma panel displays (“PDPs”), and non-emitting display devices such as liquid crystal displays (“LCDs”) requiring an external light source.
An LCD includes two panels provided with field-generating electrodes and a liquid crystal (“LC”) layer having dielectric anisotropy interposed therebetween. The field-generating electrodes supplied with electric voltages generate an electric field across the LC layer, and the light transmittance of the LC layer varies depending on the strength of the applied field, which can be controlled by the applied voltages. Accordingly, desired images are displayed by adjusting the applied voltages.
The light for an LCD may be provided by lamps equipped at the LCD or may instead be natural light.
Since optical characteristics of the liquid crystal within the LC layer are changed based on temperature, a temperature variation of the LCD has to be considered for improving reliability thereof.
That is, since the optical characteristics such as refractive index, dielectric constant, coefficient of elasticity, and viscosity of the liquid crystal are in inverse proportion to thermalization energy of liquid crystal molecules within the LC layer, values of the optical characteristics decrease as the temperature of the liquid crystal becomes higher. Thus, to optimize a state of the liquid crystal for good driving of the LCD, the temperature variation of the LCD due to internal heating and temperature within the ambient environment has to be detected.
A temperature sensor is disposed on a printed circuit board (“PCB”) mounted with a plurality of driving circuits to detect a temperature variation of the LCD. However, the PCB is generally disposed on a rear side of the LCD, on which the lamps and electric elements generating heat are disposed, instead of a front side thereof, on which the LC layer is installed, adjacent to the outside. Thus, the temperature sensor detects a temperature at the rear side which has a large temperature deviation caused by the heat. As a result, since the detected temperature by the temperature sensor has a large difference with respect to a temperature of the LC layer, temperature compensation of the LCD based on the temperature of the LC layer is not precisely achieved. In addition, since the temperature sensor is separately installed on the PCB, design redundancy of the LCD and manufacturing cost are increased.